1. Field of the Invention
The present invention relates to a technique for imaging apparatuses, such as digital cameras and digital video cameras, to prevent deterioration in image quality due to a foreign substance that is adhered to an optical element, such as an optical low-pass filter, disposed in front of the image sensor and that is captured in a shot image.
2. Description of the Related Art
In recent years, cameras have been rapidly digitalized. Especially, there have been widely used digital single lens reflex cameras, which have an optical arrangement similar to that in conventional single lens reflex cameras. In the digital single lens reflex cameras, film is replaced with an image sensor that performs photoelectric conversion.
The digital single lens reflex cameras do not require film winding operation and film exchange operation. Accordingly, in an operation of exchanging a shooting lens, once a foreign substrate, such as dust, intrudes into the vicinity of the image sensor, the foreign substance continues to appear in captured images. Accordingly, the quality of the series of the shot images is decreased.
Japanese Patent Application Laid-Open No. 2002-204379 discusses a method for removing a foreign substance in an imaging apparatus. In the method discussed in Japanese Patent Application Laid-Open No. 2002-204379, by operating a dust prevention element disposed in the vicinity of an imaging plane, a foreign substance adhered during operation such as lens exchange can be removed. Therefore, the user does not need to perform cleaning operation using a blower. As the result, a high-quality image can be easily obtained.
Japanese Patent Application Laid-Open No. 2004-172820 discusses a method for detecting a foreign substance from a plurality of images. In the method discussed in Japanese Patent Application Laid-Open No. 2004-172820, invariant contrast portions across a plurality of images that are preliminarily acquired by a user are detected.
Then, based on the information of the detected invariant contrast portions, the position of a foreign substance is detected. The user appropriately removes the foreign substance using a cleaning mode, and performs shooting. Thus, a high-quality image can be obtained.
However, in the technique discussed in Japanese Patent Application Laid-Open No. 2002-204379, it is necessary to newly provide the dust prevention element, and the production cost increases. Further, a structural space for the dust prevention element is required, and this causes increase in the size of the overall camera.
Further, in Japanese Patent Application Laid-Open No. 2004-172820, the user has to perform the foreign substance removal operation using the cleaning mode or the like in advance. Then, in spite of the operation, depending on the type of the foreign substance, the foreign substance may not be removed.
The present invention has been made to solve the above-mentioned problems, and is directed to effectively preventing deterioration in image quality due to a foreign substance that exists on an optical element such as an optical low-pass filter disposed in front of an image sensor and that is captured in a shot image.